The first book is called Allegiance: Fort Sumter, Charleston, and the Beginning of the Civil War. Allegiance is a narrative of the events in Charleston that led up to the bombardment of Fort Sumter. The larger picture is discussed but the focus is on the city of Charleston and on Fort Sumter. Great pains are therefore taken to explain the details of life in antebellum Charleston and life in a fort in the pre Civil War army. This focus on the minute details of life in Charleston harbor give the book a tense, claustrophobic feel; just like I suspect things felt in charleston in 1860.
The second book Maury Klein's Days of Defiance: Sumter, Secession, and the Coming of the Civil War. Klein's tale gives a much broader view of the events leading up to the start of the Cvil War. Defiance explores the pre-inauguration and early days of Abraham Lincoln's presidency and the early days of the Confederacy. Klein also takes time to explore the wider political issues that swirled about the start of the Civil War. When I say wider political issues I don't mean to imply that something other than slavery caused the Civil War. What I mean to say is the Klein explores the politics and culture of South Carolina and that culture led many South Carolinians to favor secession. Klein also explore the debates in Washington about various plans to compromise and how those debates paralyzed Congress and tore apart the administration of James Buchanan. Ultimately, the political debate was paralyzed because the debate over slavery could not be separated from the debate over secession and there was no compromise to had on the issue of secession.
I found two people who played major parts in the drama to be particularly fascinating. The first is Major Robert Anderson who was the commander of the Union forces at Fort Sumter. Anderson was a southerner who was friends with Jefferson Davis, married into a slave holding family, mentored the Confederate general opposing him, but somehow managed to be a stuanch unionist and refused to surrender the fort. The second person I found fascinating was South Carolina Senator James Henry Hammond. Hammond is best know for his "Cotton is King" speech that gave the broad view to the importance of a slave based plantation economy to the South. Hammond's personal life contained the contradictions the also gripped the South. Hammond was so hemmed in by the stifling life among the South's elite that he turned to taking some of his slaves as mistresses and to engaging in inappropriate relationships with his 2 nieces; who just happened to be the daughters of the Wade Hampton who was perhaps the richest and most powerful man in the entire state. Hammond's life became a metaphor for the hypocrisy that lay at the heart of southern antebellum culture.
Both of these books are good by themselves and together they give a great view of the events leading up to Fort Sumter. However, if you can only choose one then I would recommend Days of Defiance.